Teruo Ogawa

Bacon Ke, who did pioneering research on the primary photochemistry of photosynthesis, was born in China on July 26, 1920, and currently, he is living in a senior home in San Francisco, California, and is a centenarian. To us, this is a very happy and unique occasion to honor him. After providing a brief account of his life, and a glimpse of his research in photosynthesis, we present here “messages” for Bacon Ke@ 100 from: Robert Alfano (USA), Charles Arntzen (USA), Sandor Demeter (Hungary), Richard A. Dilley (USA), John Golbeck (USA), Isamu Ikegami (Japan), Ting-Yun Kuang (China), Richard Malkin (USA), Hualing Mi (China), Teruo Ogawa (Japan), Yasusi Yamamoto (Japan), and Xin-Guang Zhu (China).

A novel NDH-1L-CpcG2-phycobilisome-PSI supercomplex essential to cyclic electron transport was identified in Synechocystis sp. strain PCC 6803.

A 10-kD cytoplasmic protein, Ssl3829, plays an important role in NDH-1 assembly by accumulating subunit maturation factor and assembly intermediate in a cyanoba

Two major complexes of NADPH dehydrogenase (NDH-1) have been identified in cyanobacteria. A large complex (NDH-1L) contains NdhD1, NdhF1, and NdhP, which are absent in a medium size complex (NDH-1M). They play important roles in respiration, NDH-1-dependent cyclic electron transport around photosystem I, and CO₂ uptake. Two mutants sensitive to high light for growth and impaired in cyclic electron transport around photosystem I were isolated from the cyanobacterium Synechocystis sp. strain PCC 6803 transformed with a transposon-bearing library. Both mutants had a tag in an open reading frame encoding a product highly homologous to NdhQ, a single-transmembrane small subunit of the NDH-1L complex, identified in Thermosynechococcus elongatus by proteomics strategy. Deletion of ndhQ disassembled about one-half of the NDH-1L to NDH-1M and consequently impaired respiration, but not CO₂ uptake. During prolonged incubation of the thylakoid membrane with n-dodecyl-β-d-maltoside at room temperature, the rest of the NDH-1L in ΔndhQ was disassembled completely to NDH-1M and was much faster than in the wild type. In the ndhP-deletion mutant (ΔndhP) background, absence of NdhQ almost completely disassembled the NDH-1L to NDH-1M, similar to the results observed in the ΔndhD1/ΔndhD2 mutant. We therefore conclude that both NdhQ and NdhP are essential to stabilize the NDH-1L complex.

Summary: Simultaneous catabolic and anabolic glucose metabolism occurs in the same compartment during photomixotrophic growth of the model cyanobacterium Synechocystis sp. PCC 6803. The presence of glucose is stressful to the cells; it is reflected in the high frequency of suppression mutations in glucose‐sensitive mutants. We show that glucose affects many cellular processes. It stimulates respiration and the rate of photosynthesis and quantum yield in low‐ but not high‐CO ₂ ‐grown cells. Fluorescence and thermoluminescence parameters of photosystem II are also affected but the results did not lend support to sustained glucose driven over reduction in the light. Glucose‐sensitive mutants such as Δ pmgA (impaired in photomixotrophic growth) and Δ hik31 (lacking histidine kinase 31) are far more susceptible under high than low air level of CO ₂ . A glycine to tryptophan mutation in position 354 in NdhF3, involved in the high‐affinity CO ₂ uptake, rescued Δ pmgA . A rise in the apparent photosynthetic affinity to external inorganic carbon is observed in high‐CO ₂ ‐grown wild‐type cells after the addition of glucose, but not in mutant Δ pmgA . This is attributed to upregulation of certain low‐CO ₂ ‐induced genes, involved in inorganic carbon uptake, in the wild type but not in Δ pmgA . These data uncovered a new level of interaction between CO ₂ fixation (and the CO ₂ ‐concentrating mechanism) and photomixotrophic growth in cyanobacteria.

A mutant (Δ5) of Synechocystis sp. strain PCC 6803 constructed by inactivating five inorganic carbon sequestration systems did not take up CO₂ or HCO₃⁻ and was unable to grow in air with or without glucose. The Δ4 mutant in which BicA is the only active inorganic carbon sequestration system showed low activity of HCO₃⁻ uptake and grew under these conditions but more slowly than the wild-type strain. The Δ5 mutant required 1.7% CO₂ to attain half the maximal growth rate. Electron transport activity of the mutants was strongly inhibited under high light intensities, with the Δ5 mutant more susceptible to high light than the Δ4 mutant. The results implicated the significance of carbon sequestration in dissipating excess light energy.

Cyanobacteria possess functionally distinct multiple NADPH dehydrogenase (NDH-1) complexes that are essential to CO₂ uptake, photosystem-1 cyclic electron transport and respiration. The unique nature of cyanobacterial NDH-1 complexes is the presence of subunits involved in CO₂ uptake. Other than CO₂ uptake, chloroplastic NDH-1 complex has a similar role as cyanobacterial NDH-1 complexes in photosystem-1 cyclic electron transport and respiration (chlororespiration). In this mini-review we focus on the structure and function of cyanobacterial NDH-1 complexes and their phylogeny. The function of chloroplastic NDH-1 complex and characteristics of plants defective in NDH-1 are also described for comparison.

This minireview focuses on the mechanism of inorganic carbon uptake in cyanobacteria and in particular the two CO2-uptake systems and two bicarbonate transporters recently identified in Synechocycstis...